It is estimated that over 100,000,000 Americans currently participate regularly in at least one physical sport or conditioning activity. Physical fitness has now become a permanent part of the life of millions of people. Nonetheless, the equipment available for use in conditioning has not developed significantly. Typical types of equipment include weight machines, exercise bicycles, rowing machines, treadmills, home gyms, etc. Although these products are of some utility, they have significant drawbacks. For instance, they do not provide functional conditioning, i.e., they condition muscles to operate the equipment, but not necessarily to run, walk, swim, golf or play tennis. Moreover, most current physical fitness equipment is not only heavy, bulky and expensive, but also timeconsuming, boring and sometimes even dangerous to use.
With the advent of greater emphasis in physical fitness, a corresponding increase in musculoskeletal injuries has occurred, especially to the knee, ankle, elbow, wrist and other body joints. According to the National Center for Disease Statistics, in 1985 over 420,000 knee injuries requiring orthopedic treatment were reported. In addition, over 340,000 serious musculoskeletal injuries to the ankle, elbow, shoulder and other joints were reported.
Part of a typical process for rehabilitating an injured body joint is to flex and exercise the joint under controlled load levels. This treatment is usually given at the facilities of a physical therapist or clinic specializing in sports-related injuries. Sophisticated, expensive machines have been developed for use in rehabilitating the muscles, ligaments and other tissues of an injured or otherwise damaged body joint. However, to use these machines the patient must leave his place of employment or home to travel to the office or clinic of the therapist or sports medicine doctor. Examples of specialized, stationary machines that have been designed for conditioning and rehabilitating body joints are disclosed in U.S. Pat. Nos. 3,495,824, 4,407,496 and 4,436,303.
Some less bulky devices also have been developed for exercising or rehabilitating body joints. In one such type of device, two pivotally connected lever arms are strapped to the two limbs of the body joint. A brake mechanism is attached to and extends laterally outwardly from the pivot arms to resist the relative movement of the arms and, thus, impart a resistance force against movement of the body joint. Two examples of this type of device are disclosed by U.S. Pat. Nos. 2,832,334 and 3,976,057. As with the specialized, stationary conditioning and rehabilitating machines noted above, these devices, though less bulky, still suffer from the drawback that they are useful only for specific exercises, rather than during normal work or other daily activities.